Gas-phase conversion of glycerol to synthesis gas over carbon-supported platinum and platinum-rhenium catalysts

The rate of glycerol conversion to H-2/CO gas mixtures was measured under kinetically controlled reaction conditions over carbon-supported platinum and platinum-rhenium catalysts. The reaction is fractional order with respect to glycerol and zero order with respect to hydrogen, with activation barriers of 60-90 kJ mol(-1). The addition of an equimolar amount of Re to Pt/C increases the production rate of CO by a factor of 5 at low conversion (<20%) and while co-feeding H-2, both of these factors leading to low pressures of CO in the reactor. At higher conversion conditions (20% conversion to gas-phase products) and without co-feeding H2, the Pt-Re/C catalyst is an order of magnitude more active than Pt/C. Accordingly, Re has a greater promotional effect on the rate of glycerol conversion at conditions leading to higher CO pressures, suggesting that the primary promotional effect of Re is to weaken the interaction of CO with the surface, thereby decreasing the CO coverage and allowing the catalyst to operate at high rates in the presence of gaseous CO. Temperature-programmed reduction (TPR) studies of carbon-supported Pt and Re catalysts showed a peak near 460 K for Pt/C and near 650 K for Re/C. The position of the TPR peak for Re shifted to lower temperature on addition of Pt to Re, suggesting interaction between Pt and Re species, leading to alloy formation. (C) 2007 Elsevier Inc. All rights reserved.